Electric clock system



June 1930- H. E. WARREN ELECTRIC CLOCK SYSTEM Filed Jan. 24, 1928 2 Sheets-Sheet 1 l/Zf H Q Ma nw vE hu n e H.

Hi 5 Attorneg.

Patented June 24, 1930 UNITED STATES PATENT OFFICE HENRY E. WARREN, OF ASI-ILAND, MASSACHUSETTS, ASSIGNOR TO WARREN TELE- CHRON COMPANY, OF ASHLAND, MASSACHUSETTS, A CORPORATION OF MAINE.

ELECTRIC CLOCK SYSTEM Application filed January 24, 1928.

My invention relates to electric clock systems in which one or more secondary clocks are driven by synchronous motors connected to av source of alternating current. More particularly my invention relates to an improved method and apparatus for resetting the secondary clocks after an appreciable interruption in the current supply.

In electric clock systems it is desirable that each secondary clock indicate correct time. If these clocks are driven by synchronous motors their rate is directly proportional to the frequency of the alternating current supply and the time indicated is correct only if the frequency has remained constant at the value for which the clock gearing is designed and if the current has not been interrupted.

By means of improved regulating and generating equipment it is now possible to maintain substantially constant frequency on commercial power systems. Interruptions in service, however, due to lightning, short circuits and other causes well known to those skilled in the art are practically unavoidable. It is, therefore, desirable to equip electric clock installations with means for quickly resetting the secondary clocks, as soon as current is again available, after an interruption.

The primary object of my invention is to provide simple and efiicient apparatus for temporarily increasing the speed of the secondary clocks, after every appreciable interruption in service, until they again indicate correct time.

The features of my invention which are believed to be novel and patentable are set forth in the appended claims. My invention both as to its organization and method of operation together with further objects andadvzmtages thereof, will best be understood by reference to the following description taken in connection with the accompanying drawings in which Figs. 1 and 2 are front and side views respectively, of the resetting device; Fig. 3 is a detail view of part 73 shown in Figs. 1 and 2; Fig. 4 is a schematic diagram of an electric clock sysfem equipped with my resetting mechanism- Serial No. 249,175;

'; d Fig. 5 is a modification of my invention, in which I provide a separate source of high frequency current to energize the motors during the resetting operation.

Figs. 1 and 2 show the resettin device comprising a spring operated cloc mechanism, usedas a master clock or timing device, arranged to be bodily rotated by either of two motors, a pointer operated by the clock and a switch actuated by the pointer. Referring to these figures more in detail, indicates a standard marine clock movement supported between plates 11 and 12. All details of this movement are not shown. The main driving spring is located inside of drum 13 and is wound by means of shaft 14 extending through plate 12. A gear 15 is rigidly mounted on the end of this shaft. The minute hand shaft 16 also extends through plate 12 and operates a pointer 17 and pinion 18. The clock movement 10 is mounted on a large gear 19, so that the axis of the minute shaft is in alignment with the center of the gear. On the other side of the gear 19, extending perpendicularly to it, a sleeve 20 is provided, whose axis is also in line with the center of the gear. It is fitted loosely over shaft 21 which in turn is rigidly mounted on base plate 22. The entire clock movement may thus be rotated as a unit, about an axis which coincides with the axis of the minute shaft. Sleeve 20 is held in place over shaft This train of gears is so proportioned that normally the spring is wound at the same rate that it unwinds, whereby it is main tained at a constant. tension.

Gear 19 is arranged to be driven counterclockwise by either of two motors 28 or 29 through an epicyclic gear train. The motors are preferably of the self-starting synchronous type such as is described in my Patents 1,283,432, 1,283,434, and 1,283,435. Motor 28 drives gear 19 at a normal rate of one revolution per hour by means of gear 30 mounted on its shaft and engaging gear 31. Gear 31 drives a pinion 32. Pinion 32 engages gear 33 which revolves on a shaft mounted on gear 31 and drives back gear 35 which is also mounted on the same shaft and is attached to gear 33. Back gear 35 engages and drives gear 36 which in turn drives gear 38 by means of shaft 37011 which both are rigidly mounted. Gear 38 finally engages and drives gear 19. Under normal conditions gear 34 is stationary but during the resetting conditions motor 29 also drives gear 19 counter-clockwise by means of gear 39 mounted on its shaft and engaging gear 34 on which back gear 35 and gear 33 are mounted. The rotation of gear 31 causes back gear 35 and gear 33 to travel in a circular path the center of which is shaft 37. This motion of gears 33 and 35 causes gears 36 and 38 and, therefore, gear 19 to travel at a rate which is fast enough for quick times as great as that caused by the rotation of 33 and 35 about their own axis when driven by motor 28.

Pointer 17 is operated clockwise by the master clock mechanism at the rate of one revolution per hour thus corresponding to the minute hand of a clock. During normal operation of motor 28 this pointer, therefore, remains stationary at any predetermined position. But when motor 28 stops due to an interruption in service pointer 17 will immediately move clockwise. The angular distance that it moves from its normal position is, therefore, a measure or integration of the interruption of service or of the negative frequency error and if the motors of the secondary clocks stopped at the same time. this distance is also equal or proportional to that which the minute hands of these clocks should be set ahead to indicate correct time. Therefore, in order that the position of this pointer 17 may control the resetting of the secondary clocks I cause it to actuate a switch as hereinafter described in connection with Fig. 4, and I connect the motors of this resetting device to the source from which the secondary clock motors are energized.

Fig. 4 shows, diagrammatically an electric clock system equipped with a resetting device such as illustrated and described in connection with Figs. 1 and 2. The second ary clocks are each equipped with two motors, only the connections to which are indicated, which operate the clocks through an epicyclie gear transmission, not shown, such as that described and illustrated in Figs. 1 and 2. This transmission is of the same ratio as that of Figs. 1 and 2, so that during the resettin operation the ratio of movement of the clocks to that of normal is exactly as the resetting purposes, for example ten ratio of the resetting operation of the gear 19 of Figs. 1 and 2, to normal. Referring now in detail to this figure, 10 and 11 indicate the incoming lines from any suitable commercial source of alternating current. The secondary clocks are indicated at 42 each having three conductors leading to it.

The conductor indicated as leading to the top of each secondary clock, is common to both motors and is permanently connected to incoming line 10 through conductor 1 Each of the two conductors indicated as leading to the bottom of each secondani' clock leads to one of the two motors in the clock. One of them. is connected to common conductor 1 1 which in turn is connected to line 11 through switch 47. This makes a complete and permanent circuit through one of the motors of each secondary clock. The terminals of motor 28 are also permanently connected. to lines 10 and ll through conductors 43 and 58 so that this motor and the set of motors of the secondary clocks just mentioned are the motors that normally operate the gear 19 and the secondary clocks. I shall, therefore, refer to these secondary clock motors as the motors corresponding to motor 28. The third conductor leading to each secondary clock is connected to a common conductor 48, which is connected to a conductor 57, through a switch 47 to terminal 60 of a switch 16. To this same terminal one terminal of motor 29 of the resetting device is connected so that at a closing of switch 46 a circuit is made both to motor 29 and this latter set of secondary clock motors. I shall, therefore, refer to these secondary clock motors as the motors corresponding to motor 29. It is now apparent that since an epicyclic gear transmission is used in each clock which has the same ratios as that used in the resetting device and since the motors corresponding to motor 28 operate the clocks at normal rate, the motors corresponding to motor 29 operate the secondary clocks, in the example given, at ten times normal rate. Switch 46 is controlled by the pointer 17 of the resetting device as I shall now explain. Pointer 17 engaged at its end a contact spring 49 which is electrically connected to one end of a magnet coil 52 which when energized closes switch 46. Contact spring 49 is so mounted between two adjustable contact posts 50 and 51 that it may be forced into contact with post 51 by pointer 17. but engages contact 50 if released. Contact post 51 is connected to conductor 43. and 50 is connected to cont-act 54 of a thermostatic switch \Vhen the installation of the resetting device is made, pointer 17 is set to force contact spring 49 in engagement with contact post 51. This position is maintained. as has already been explained, as long as motor 28 is energized and operates. As soon as motor 28 is deenergized and stops, pointer closed during the transition of contact 17 will move clockwise due to the operation of the clock mechanism and thereby releases contact spring 49 which then makes contact with contact post 50. An electric circuitis thereby established from line through 43, to which one end of magnet coil 52 is connected, through coil 52, spring 49, contact to'contact 54 of switch 53. Switch 53 is a thern'iostatic element heated by a coil connected to the common ,source. The circuitis, line 41 conductors 58 and 57, coil 55, reactance 56, conductor 43 to line 40. When coil 55 is deenergized thermostat 53 cools and flexes toward contact 54. The time that 53 takes to cool and engage contact 54 can be adjusted to any suitable value. and constitutes the shortest time for which resetting is desired. The switch 53 is not essential and may be omitted in which case 50 will be connected directly to line 58. Switch 53 is employed to prevent frequent operations of the clock resetting device due to slight variations in the normal frequency supply and failures of momentary duration. When the clock system is connected to an unregulated source it is advisable to omit this switch 53 so as to allow resetting due tofrequency errors only.

\Vhen in the case of a service interruption 53 cools and engages contact 54, a circuit is established which connects magnet coil 52 to the power source. This circuit is from line 40, conductor 43, coil 52, spring 49, contacts 50 and 54, thermostat 53, conductor 57 to which it is electrically connected, to conductor 58 and line 41. \Vhen power is again available coil 52 will be energized and will close switch 46 against the action of a spring 59. This closing of switch 46 energizes motor 29 and the corresponding secondary clock motors. The circuits may be traced from line 41, conductor 58, switch 46, motor 29, conductor 43 to line 40; and for the secondary clock motors, line 41, conductor 58,

. switch 46, switch 47, conductor 57, bus 48,

through the motors to bus 43 and line 40. As already stated the energization of motor 29 and the corresponding clock motors causes gear 1.9 and the clock hands to be operated at tentimes normal rate. Pointer 17 therefore moves back toward the position at which it was originally set and the secondary clocks.

advance toward, the correct indication. When pointer 17 strikes spring 49 on its return ourney it breaks the circuit between 49 and contact 50. This, however, does not deenergize C011 52 since. at the closing of switch 46 a resistance 61 is connected in shunt to 49 and One end of resistance 61 is permanently connected to coil 52 at the terminal to which spring 49 is connected, and the other end is connected to line 41 through conductor 58 when switch 46 is closed. This serves the purpose of holding switch 46 higher spring 49 from contact 50 to 51 and to avoid a short circuit at the instant 49 engages contact 51. At that instant the ends of coil 52 are electrically connected by means of conductors 43 and 71 whereby the coil is deenergized. At this same instant the resistance 61 is connected across lines 40 and 41 through conductors 43, 71 and 58. Switch 41, however, opens very quickly after coil 52 is deenergized and the circuit is broken. Motor 29 and the corresponding secondary clock motors are deenergized the moment that switch 46 opens. The pointer 17 is then in its normal and predetermined position again, the secondary clocks indicate the correct time, and continue to operate at the normal rate. If for any reason manual resetting is required switch 47 is so arranged that the motors corresponding to motor 29 may be energized at will.

In Fig. 5 I have shown a modification of my invention in which I omit the resetting motor and epicyclic gear transmission used on the resetting device and the secondary clocks of Fig. 4 and provide instead, a frequency converter to supply current of than normal frequency during the resetting operation. The modification shown in Fig. 5 is described and claimed in my divisional application Serial No. 368,270, filed June 4, 1929. I have indicated in this figure motor 28 which as in Fig. 4 drives gear '19 at the rate of one revolution per hour when energized from the power lines 40 and 41. Pointer 17 engages spring 49 and operates as 'described'in connection with Fig. 4. The circuit through coil 52 is also established in exactly the same manner as described in Fig. 4. When power is again available after an interruption switch 46 is closed and connects motor 62 of the fre .quency converter to the source, the circuit being, line 41, conductor 58, switch 46, motor 62, conductor 43 to line 40. This motor then starts and drives generator63. \Vhen this generator builds up its voltage, magnet coil 64 connected across its terminals is energized and actuates switch 65. Switch 65 is a double throw switch which, when coil 64 is deenergized, is held against contact 66 by the action of spring 67, thereby causing motor 28 and the secondary clock motor to lot) ill!

be energized from the lines 40-41. W'hen coil 64 is energized, 65 makes contact with 72 which is connected to one terminal of the generator. The other terminal of the generator is permanently connected to one terminal of the clock motors and motor 28, through conductor 43. The motor'28 and the clock motors are therefore supplied by this generator during the resetting eriod. The frequency of this curreut is pre erably twice that of the commercial source. The clocks and gear 19 are, therefore, operated at twice normal rate until pointer. 17 has again reached its normal position. The cycle of this operation is exactly the same as that described in Fig. 4. When switch 46 opens, however, it opens the circuit to the motor of the frequency converter which stops. As soon as generator 63 stops coil 64 is deenergized, switch 65 opens and connects motor 28 and the secondary clock motors to the commercial source whereupon normal operation is resumed.

Fig. 3 shows an attachment to the resetting device shown in Figs. 1 and 2 to'take care of an interruption in service lasting longer than one hour. It is evident that if power is off more than one hour the pointer 17 will have made one complete revolution and would under normal conditions engage contact spring 49 on its reverse side, thereby breaking or otherwise becoming damaged. To avoid this I provide gear 73 suitably supported on base 22 by means of studs 75, cross piece 76 and pin 77 to engage pinion 18. This gear 73 is provided with a projecting cam surface 74 comprising eleven twelfths of a complete circle, and is set so that the pointer 17 touches the gear surface at a point between the ends of this cam surface 74 when it is in its normal position. The ratio of the pinion to the gear is 1 to 12, so that when pointer 17 and pinion 18 have made one revolution, the gear 78 has made one twelfth of a revolution and has interposed cam surface 74 between itself and the pointer. As the pointer then returns to engage spring 49 it engages cam surface 74.-

and is thereby deflected rearwardly so as to pass contact spring 49. This same action takes place for twelve consecutive revolutions .of pointer 17, if the power if off that long. After the twelfth revolution, however, the open space between the ends of the cam surface 74 is again in such position that if power were turned on at that moment the pointer would be in its normal position and noresetting would take place. If the power is off less than twelve hours and more than one, the cam surface 74 also prevents the engagement of pointer 17 with spring 49 on its return journey until the correct hour is reached.

In accordance with the provisions of the patent statutes, I have described the' principle of operation of my invention, together with the apparatus which I now consider the best embodiment thereof; but I desire to have it understood that the apparatus shown is only illustrative and that the invention can be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. An electric clock system arranged to receive energy from an alternating current source including a master clock provided with a minute hand, a synchronous motor normally energized and arranged to rotate said master clock at a speed equal and opposite to that of saidminute hand, a second synchronous \motor normally deenergized and arranged when energized to rotate said master clock at a greater speed and opposite to that of said minute hand, a switch operated by said minute hand and arranged-to control the energization of said second synchronous motor, and secondary clocks each provided with two synchronous motors arranged and connected to respectively operate said secondary clocks in synchronism with the two above mentioned rotational movements of said master clock.

2. In an electric clock system connected to a regulated frequency source'of alternating current, a secondary clock equipped with two synchronous motors one of said motors being normally energized from said system and the other being normally deenergized, gearing transmission whereby the first mentioned motor of the clock operates it at normal rate and whereby the second motor operates it at greater than normal rate when energized, and resetting mechanism responsive to interruptions of said source and energizing the second motor after each appreciable interruption in service until the clock againindicates correct time.

3. In an electric clock system supplied from an alternating current source, a secondary clock provided with a synchronous motor normally energized and arranged to operate said clock at correct rate, a resetting motor normally deenergized but arranged when energized, to operate said clock at a greater rate, a resetting device including a master time element provided with a minute hand, a synchronous motor arranged to rotate said time element at a speed equal and opposite to that of said minute hand, a resetting motor normally deenergized but arranged when energized, to rotate said time element at said greater rate, and a switch arranged to control the energization of said resetting motors and maintained in a deenergizing position by said minute hand only when said secondary clock indicates correct time.

4. In a secondary clock system operated from a source of electric energy, apparatus for correcting said system after an interruption in said source comprising a master clock having a pointer operated thereby, said clock being mounted to rotate about the axis of rotation of said pointer, motor means supplied from said source and arranged to bodily rotate said clock in a direction opposite to the normal movement of said pointer at a normal rate such that the pointer remains stationary in a given position as long as said source remains uninterrupted, and means controlled by the move-. ment of said pointer, caused by the stopping of said motor means due to an interruption in said source and the continuous operation of said master clock, for correcting the secondary clock system.

5. In a secondary :clock system operated from a source of electric ener apparatus for correcting said system a ter an interruption in said source comprising a master clock having a pointer operated thereby, said clock being mounted to rotate about the axis of rotation of said pointer, motor means supplied from said source and arranged to bodily rotate said clock in a direction opposite to the normal movement of said pointer at a normal rate .such that the pointer remains stationary in a given position as long as said source remains uninterrupted, means controlled by the movement of said pointer, caused by the stopping of said motor. means due to an interruption in said source and the continuous operation of said master clock, for correcting the secondary clock system and means for permitting the correctin means to function only when the interruption was of an appreciable duration.

6. In an electric clock system connected to a source of alternating current, including secondary clocks operated by synchronous motors, a resetting control device comprising a master clock operating a minute hand having a predetermined normal position,

such motor is energized, means for'measuring the negative integrated .frequency error of the system and means controlled thereby for energizing the second mentioned motor.

9. A clock system comprising a source of alternating current, a master clock and a secondary clock, a synchronous motor connected to said system for normally operating said secondary clock at normal rate, a synchronous motor, connected to said system and associated with said master clock for measuring errors in the time indicated by said secondary clock as compared to said master clock, circuit controlling means operated by said master clock in response to such error measurements, and synchronous resetting motors respectively associated with the secondary clock and the master clock and energized by said circuit controlling means and adapted when so energized to respectively operate the secondary clock at greater than its normal rate and to produce a corresponding corrective movement in said error measuring apparatus.

In witness whereof, I have hereunto set my hand this 20th day of J an., 1928.

HENRY'E. WARREN said master clock being normally rotated bodily at a rate equal to and opposite to the rotation of said minute hand, a synchronous motor for rotating said master clock also connected to said source, a switch operated -by said minute hand when said master clock stops or fails to rotate at normal speed,

neans controlled by the operation'of said switch for simultaneously and equally increasing the .rate of the secondary clocks and the rotation of the master clock .until the said minute hand is in its predetermined position.

7. In an electric clock system comprising an alternating current circuit, an electrically operated secondary clock connected to said circuit in such manner as to be normally operated at a rate proportional to the frequencyof said circuit, a normally deenergized synchronous motor adapted when energized to drive said secondary clock at a, faster rate than normal, master clock means for measuring the integrated frequency error of said system and means controlled thereby in response to such error for energizin said synchronous motor.

8. In a clock system'comprisin an alternating current source, a secon ary clock provided with two synchronous operating motors, one motor being normally connected to said system to operate the clock at correct rate when-the frequency of the. source is normal and the other motor being normally deenergized but geared to the clock to drive it at a greater rate than normal when 

